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Teensy I/O's ot 5V tolerant

Hi,

since in general the Teensy inputs/outputs are not 5V tolerant, but most of the shield, sensors, actors e.g. for Arduino work with 5V signals, I'm curious what most of you are using (voltage level shifters, opto couplers?). Problem in may cases are space considerations for the final project or even timing issues if the level shifters are not fast enough. Would appreciate every comment on the topic.

Teensy I/O's ot 5V tolerant

Hi defragster,

tanks a lot for the fast reply. I need a bunch of I/O's and got recently a 3.6, which I planned to use for the project. Have an 3.2 as well, but this way not enough I/O's. So, seems like level switching is the only alternative - right?

Cheers,

Peter

Originally Posted by defragster

True : Teensy LC and 3.6 are 3.3V devices

Teensy 3.2 and 3.5 are 5V tolerant devices.

Not sure which Teensy is in use here? If picking a 5V tolerant part is an option that could limit the level shifting issues.

If you don't need the absolute fastest CPU and you don't need the USB host controller, a Teensy 3.5 would suffix for digital inputs.

On both the 3.2 and 3.5, all pins that can do digital input, will work with 5v inputs. Digital outputs will remain at 3.3v. The analog input pins that also support digital inputs will allow 5v, but anything above 3.3v will register as 3.3v. The analog input pins that cannot do digital functions (A10, A11, etc.) are only 3.3v, and you may damage your Teensy if you feed it more than 3.3v. The reset, program, and Vbat pins are also 3.3v only.

you could use the SPI/I2C library i contributed here which can link several SPI/I2C teensies together if you need more gpios, adding a 3.5 to your 3.6 would get you 5v tolerant digital pins on the extra gpios accessible, or just get a few port expanders, preferably the SPI versions as they are very fast

Can also be worth a look at those Arduino '5V' parts. Many of the current ones are actually natively 3.3V or even lower for the same reason Teensy is 3.3V and either have level conversion built in or are just 5V tolerent so in many case work in 3.3V anyway. Obviously this means reading the documentation and potentially doing a voltage check before plugging in. Providing some info on what parts you are trying to use may help here.

Almost all shields, sensors etc. for the Arduino are internally 3.3V or have a 3.3V alternative. Save maybe for some power electronics like servos. In almost all cases a simple resistor divider will help you out, unless for something with very strict timing/slew rate requirements.

Stay away from so called 'bidirectional' level shifters like the TXB-0108 if you don't want to spend your days debugging I/O .